Optimus was just a squad leader that is thrust by the High Council of Elders into the Prime Rank against his will after Megatron kills Zeta Prime thus becoming Optimus Prime. Optimus Prime is the heroic leader of the Autobots. He is both brave and compassionate, inspiring greatness in those who follow him. Optimus has a strong sense of justice and righteousness and has dedicated himself to the protection of all sentient life; he will battle his foes with unyielding resolve to uphold his belief. Even the leader of the Decepticons, Megatron, begrudgingly admits his respect for Optimus Prime. His personality is heroic, dependable, and honorable.
War for CybertronEdit
Optimus Prime is a powerful, decorated and renowned military leader of the Autobots, and a close personal friend of the current leader, Zeta Prime. At a certain point, he saves Bumblebee from his Decepticon assailants. Unfortunately, he learns that Zeta Prime has been murdered by Megatron, leader of the Decepticons. In light of this new information, Optimus takes it upon himself to lead the Autobots in all but name against their foes and avenge his friend's death until the Autobot council can announce a successor.